A radiation monitoring device is used for the effluent management of a nuclear reactor facility, a spent fuel reprocessing facility and the like, or the radiation control in the vicinities of those facilities, or the environmental radiometry in the areas adjacent to those facilities. A radiation detector has temperature characteristics, and thereby, the wave height of the radiation, which is detected by the radiation monitoring device, fluctuates in magnitude, corresponding to the change in temperature (see Patent Documents 1-3, for reference). In order to compensate for the temperature fluctuations of the wave height, proposed is a radiation monitor which is equipped with a scintillator, a photo multiplier tube, a radiation detector, a pulse amplifier, an analog to digital convertor, a temperature sensor and a measurement section (for example, Patent Document 4).
The scintillator is equipped with a NaI (Tl) crystal and emits scintillation, if the scintillator detects radiation. The photo multiplier tube converts the scintillation into an electron, amplifies the electron, and outputs a current pulse. The radiation detector contains a preamplifier, and converts the current pulse into an analog voltage pulse to output the analog voltage pulse. The pulse amplifier receives the analog voltage pulse and amplifies it, and further, removes high frequency noises superimposed on the analog voltage pulse. The analog to digital converter receives the amplified analog voltage pulse, converts the wave height of the analog voltage pulse into a digital value, and outputs data on the wave height.
The temperature sensor detects the temperature of the radiation detector and outputs a temperature signal. The measurement section receives the data on the wave heights and the temperature signal, and calculates a dose rate and outputs the dose rate, by performing dose weighing to the data on the wave heights. Furthermore, the measurement section generates a gain control signal and outputs the signal, which is utilized for controlling the gain of the pulse amplifier based on the temperature signal. The wave height of the analog voltage pulse, which is amplified in the pulse amplifier, has fluctuations due to the temperature characteristics of the radiation detector. In the above mentioned radiation monitor, the gain of the pulse amplifier is controlled so that those fluctuations may be compensate for.
Moreover, proposed is a radiation monitor, which is focused on the characteristic of an inorganic scintillator in that the luminescent decay time of the inorganic scintillator becomes smaller with a rise in temperature (for example, Patent Document 5). In replacement of the measurement section, this radiation monitor is equipped with a rise time to temperature conversion section, which receives the output pulse of the radiation detector and measures the temperature of the radiation detector from a rise time. The gain of the pulse amplifier is controlled based on the temperature information from the rise time to temperature conversion section, and the temperature characteristics of the radiation detector are compensated in a similar manner.